The present invention relates to gear machines in general, and more particularly to reversible gear machines which can be used as gear pumps or gear motors for either direction of flow of the operating fluid through the machine.
There are already known various constructions of gear machines of the above type, which generally include a housing bounding an internal chamber and two gears with external gear teeth annuli, these gears being so mounted on the housing and accomodated in the internal chamber that the gear teeth of the annuli mesh with one another during the operation of the gear machine while the gears revolve about their respective axes. The mounting is accomplished by bearing members which support stub shafts jointly rotatable with the gears and extending beyond the axial end faces of the same. The bearing members are usually substantially sleeveshaped and separate from the housing, being supported in the internal chamber of the housing for limited axial displacement toward and away from the gears. However, it is also possible to form the bearing members integral with the housing and especially with the end walls of the housing. In either event, it is necessary to assure that the interface between the respective end face of the gears and the element axially adjoining the same be sealed so as to avoid excessive leakage of the operating fluid through the interface between the high-pressure side and the low-pressure side of the gear machine. Thus, it has already been proposed to let the pressure of the operating fluid act either on the separate bearing members at the surface thereof facing away from the gears, so that such bearing members simultaneously constitute a pressing element, or to provide a separate pressing element at the respective axial side of the gears, and to let the pressure of the operating fluid act on the surface of the separate pressing element which faces away from the gears, to thereby displace the pressing element into sealing contact with the respective end face of the gears during the operation of the gear machine, thus keeping the size of the interface to a minimum regardless of the wear. Since it is also necessary to separate the high-pressure side from the low-pressure side of the gear machine even at the surface of the pressing element which faces away from the gears, it is customary to provide a substantially eyeglass-frame-shaped sealing component at this surface, especially to accommodate the same in a groove formed usually in the pressing element. This sealing component then delimits respective pressure fields at the aforementioned surface, these pressure fields being separated from one another by the sealing component and being respectively exposed to the pressure of the operating fluid derived from the high-pressure side and from the low-pressure side of the gear machine.
In one conventional construction of the gear machine incorporating the above-discussed structural features, the openings of the bearing members in which the shafts of the gears are rotatably supported are connected with one another at the regions of the sealing components. This construction of the sealing components and the resulting configurations of the pressure fields delimited thereby have the disadvantage that the compensation of the pressures acting on the pressing element from opposite axial sides leaves much to be desired. Another important disadvantage of this conventional construction is that, because of the pressure force distribution between or among the pressure fields, the gear machine is prone to malfunction, especially when operated with reverse pressure gradient.